var subBtn = document.querySelector(".submitBtn");
subBtn.onclick = function () {
  var form = document.getElementById("form");

  var input = form.getElementsByTagName("input");
  if (input[0].value == " " || input[1].value == " ") {
    return alert("邮箱地址或密码为空！");
  }
  if (input[0].value != "123@qq.com" || input[1].value != "123456") {
    return alert("邮箱或密码错误");
  }

  if (input[0].value == "123@qq.com" && input[1].value == "123456") {
    window.location.href = "backStage.html";
  }
};
